Jonathan Clarke, King’s College London
You may imagine a “brain” as a disembodied football, but the organ is hardwired to every part of the body. This chicken embryo highlights two neuron types that will eventually separate into individual cranial nerves.
The red neurons will become the glossopharyngeal nerve, which lets parts of the tongue and upper throat feel and move. It also makes tasting possible in the back of your mouth.
The green strands will weave themselves into the body’s most complex nerve: the vagus. Named for the Latin word for wandering, it stretches down through your waist, wrapping around your stomach and other organs. This nerve lets the brain trigger the gag reflex, evaluate your “gut feelings,” and slow your pounding heart after a scare. Damage to either nerve can spell trouble, but when you open your mouth, stick out your tongue, and say “ahh,” your doctor knows they’re working properly.
Klarer, M., Arnold, M., Günther, L., Winter, C., Langhans, W., & Meyer, U. (2014). Gut Vagal Afferents Differentially Modulate Innate Anxiety and Learned Fear. The Journal of Neuroscience, 34(21), 7067. doi: 10.1523/JNEUROSCI.0252-14.2014
The Editors of Encyclopaedia Britannica. (2018). Vagus nerve. In Encyclopaedia Britannica. Retrieved from https://www.britannica.com/science/vagus-nerve
Walker, H. K. (1990). Cranial Nerves IX and X: The Glossopharyngeal and Vagus Nerves. In H. K. Walker, W. D. Hall, & J. W. Hurst (Eds.), Clinical Methods: The History, Physical, and Laboratory Examinations (3rd ed., p. Chapter 63). Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK386/